Relative importance of the atmosphere-ocean exchanges of latent and sensible heat in the generation of rainfall in the Canary Islands environment

Abstract

The aim of this study is to investigate the relationship between precipitation and the ocean Sea Surface Temperature in the Canary Islands area. Since the Canary Islands are located in the Atlantic subtropical belt under the direct influence of the Azores high and the trade winds, we will also focus on several meteorological variables involved in the process. In this context, we suggest a relationship between the Canary Island rainfall and the Atlantic large-scale circulation, characterized by the North Atlantic Oscillation (NAO) index. Some significant relationships between rainfall, SST, wind speed, atmospheric temperature and NAO index are found. The temporal variability in SST recorded in the study area coincide in many cases with southeast or big North Atlantic storms (87.5%) that feed on latent heat released by the upper ocean. In order to characterize the physical mechanisms involved, a set of automatic objective techniques for the anomalies detection (with Argo profilers) and storm identification is applied. Additionally, the NAO index shows a greater rainfall intensity displaced towards the autumn months over the years with a negative summer NAO index. The study period covers from 1951 to 2017 in the case of NAO index and meteorological variables, from 1982 to 2017 in the case of SST and from 1998 to 2017 in the case of Argo profilers’ availability. The study finally provides a comprehensive view of the mechanisms involved in the rainfall generation over the Canary Islands and its intensity variability according to the summer NAO index.